This paper presents possibilities for reducing the costs of electricity generation as a result of modernizations aimed at increasing the rated power of turbogenerators. Programs for calculating temperature fields in large AC machines have aided work on turbogenerator modernization. Turbogenerators with increased rated power operate in many power plants in Poland and abroad, e.g. in Bulgaria, Finland, Greece, Slovenia, Korea and China. The example of TWW‑200‑2(2A) turbogenerator modernization is presented. The improved fans with increased capacity have enabled the increase in the turbogenerator rated power by 20%.